In recent years, internal combustion engines, particularly diesel engines, are equipped with an exhaust micron particle collecting device (or a Diesel Particulate Filter, hereinafter referred to as DPF) for collecting exhaust micron particles (or particulate matter, hereinafter referred to as PM), and when the PM collected in the DPF reaches a prescribed amount, it raises the exhaust temperature, burns off the collected PM and regenerates the DPF. When said DPF regeneration is performed, the throttle valve is control-pressed to cause pump loss and decrease the amount of air intake, while increasing the amount of fuel injection and raising the exhaust temperature.
However, for internal combustion engines in vehicles, since blow-by gas containing water vapor is returned to the portion that is upstream of the throttle valve, this blow-by gas freezes in cold climates where outdoor temperatures are low so that when the water vapor gets in the shaft of the throttle valve, it freezes and gets stuck. Foreign matter can also clog the throttle valve and cause it to get stuck.
When the diagnostics shows that it has become fixed, the throttle control is intercepted and the amount of fuel injection is increased to become more than the amount injected during normal control in order to ensure the minimum torque and prevent the engine from stopping. (see Unexamined Japanese Patent Application Publication No. 2000-345899.)